Two abdominal radiologists in consensus (E.G and N.Z.E) reviewed the upper abdominal parts that were included in the chest CT scans and calculated the L/S. In this study, L/S was obtained from two consecutive unenhanced chest CT scans of each COVID-19 patient to assess if a change occurred in hepatic density during the course of disease. Hepatic attenuation values were calculated by placing two regions of interest (ROI) greater than 100mm2 in area, in the right liver lobe anterioposteriorly and one ROI in the left liver lobe. Splenic attenuation was obtained by placing one ROI, greater than 100mm2 in area (Fig. 1). L/S was calculated by taking the average Hounsfield unit (HU) measurement of both liver lobe ROIs and dividing it by the spleen HU value [22]. Attempts were made to place ROIs in the exact location as possible in both CT scans.
Fig. 1 29-year-old woman with COVID-19. Hepatic attenuation values were calculated by placing one ROI greater than 100mm2 in area in the left liver lobe (L1), and two ROIs, in the right liver lobe (L2 and L3). Splenic attenuation was obtained by placing one ROI, greater than 100mm2 in area (S). Liver-to-spleen ratio was calculated as [(L1 + L2 + L3)/3]/S